Throttle valve body with a tapered channel on one side of its axis and a tapered flap on the opposite side thereof

ABSTRACT

A throttle valve body (1) including a flap (6) of which the side pivoting down or up on opening has a shoulder (17) on the flap surface facing upwards or downwards, respectively, defining a gradually widening cross-sectional area with the cylindrical (7) or frusto-conical (9) wall opposite the intake channel (3) through the housing (2). The side of the flap (6) which rotates up or down, respectively, on opening consists of a flat half disk of which the edge is , at first, opposite a tapered surface portion (14) with a complex shape to define a gradually widening cross-sectional area downstream from an inlet convergent (15,12) and upstream from an outlet divergent, respectively.

The invention relates to throttle valve bodies for a fuel injectiondevice of an internal combustion engine and has, more particularly, asits subject a throttle valve body comprising a housing, in which an airintake duct is formed, and comprising a flap in the form of asubstantially circular or slightly elliptic disk, which is mounted on acenter axis of rotation transverse to the duct and which is displaceablebetween a minimum, if appropriate zero, opening position and a maximumopening position, in which the plane of the flap is orientedsubstantially parallel to the axis of the intake duct, in order toregulate the airflow which is admitted into the engine and to which thefuel quantity injected for each engine cycle must be linked.

The most commonly used throttle valve bodies comprise a flap, in theform of a thin circular disk of constant thickness, and a duct in theform of a circular cylinder in the zone where the flap pivots, thepassage cross section offered to the air between the flap and the wallof the duct varying rapidly from the minimum opening position of theflap during the initial angular displacement of the latter, above allwhen said minimum opening position is virtually zero.

Now in order to control the engine satisfactorily, that is to say so asto ensure driving comfort, under low loads (that is to say, for smallopenings of the flap), the initial increase in the passage cross sectionas a function of the position of the flap must be highly progressive.

In order to obtain the requisite progressiveness, bodies have alreadybeen provided which use a flap of complex shape (FR-A-2,674,573), whichis much less advantageous than the conventional flap in the form of asimple disk, and/or a duct, the wall of which has at least one portionof complex shape (FR-2,663,710 and FR-A-2,694,963), which is costly toproduce by the machining and/or casting of metal parts or which isdifficult to produce by molding synthetic materials because of the needto use multiple or removable cores.

FR-A-2,674,573 describes a throttle valve body, as defined above, inwhich that side of the flap which rotates upstream from the minimumopening position has, on its downstream face, a bulge of a cross section(in a plane orthogonal to the axis of rotation) sufficiently small toallow the flap to rotate. That side of the flap which rotates downstreamduring opening and the duct cross section downstream of the minimumopening position of said side rotating downstream have, in generalterms, shapes which cooperate in order to impart to the cross sectionfor the passage of air between them a law of variation as a function ofthe angle of rotation, the initial gradient of which is lower than themaximum gradient of the law of variation during opening. This isobtained by causing to rotate, in an intake duct in the form of acircular cylinder in the zone of rotation of the flap, a flap, of whichthe side which rotates downstream during opening carries, on itsupstream face, a bulge which may be symmetrical, with respect to theaxis of rotation, to that on the downstream face of the flap siderotating upstream, each bulge being a flyweight attached to the flap ora shoulder in one piece with the latter, the edge of bulge having aprofile selected so as to slow the increase in the passage cross sectionduring the initial opening of the flap.

However, it is also possible for the flap side rotating downstream to bein the form of a thin half disk and for the intake duct to have, fromthe minimum opening position of the flap, a portion with a circularcross section decreasing downstream, thus causing a flap of complexshape to cooperate with an intake duct having a wall of complex shape.

FR-2,663,710 describes a throttle valve body, as defined above, theintake duct of which has, both upstream and downstream of the axis ofrotation, a portion, one half of which is semicircular and of constantradius and the other half of which has, at each level along the axis ofthe intake duct, a cross section in the form of an ellipse, the complexsurface of elliptic cross section located respectively upstream anddownstream of the axis of rotation being on that side of the flap whichpivots respectively upstream and downstream during opening.

FR-A-2,694,963 describes a throttle valve body, as defined above and ofthe type in which that side of the flap which rotates respectivelyupstream and downstream from the minimum opening position is in the formof a flat half disk and the intake duct has a wall which, on that sideof the flap which is in the form of a flat half disk and respectivelyupstream and downstream of the minimum opening position of the flap, hasan evolutive surface portion of complex shape cooperating with this flapside in the form of a flat half disk, in such a way that, at the startof the opening of the flap, the passage cross section delimited betweenthem increases as a function of the opening angle less rapidly than inthe case of a cylindrical duct.

According to FR-A-2,694,963, this is obtained due to the fact that theintake duct has a straight cylindrical portion having a cross sectioncorresponding to the shape of the flap in the minimum opening position,said portion extending upstream and downstream of this minimum openingposition, and has, upstream and downstream of the cylindrical portionand along the path followed by the upstream and downstream edges of theflap as far as a definite opening angle of the latter, respective zoneswhich are delimited by circle arcs centered on the axis of the intakeduct and having radii decreasing from the cylindrical portion and whichthus form two evolutive surface portions of complex shape which may besymmetrical to one another with respect to the axis of rotation andwhich each cooperate respectively with one of the two flap halves in theform of a flat half disk.

The disadvantages of the throttle valve bodies of the prior artpresented above are their production cost when they are made of metal,the complexity involved in the production of their mold and thedifficulties encountered during removal from the mold, when thesethrottle valve bodies are molded from a synthetic material, for examplea thermoplastic. In particular, molding throttle valve bodies accordingto FR-2,663,710 and FR-A-2,694,963 from synthetic material makes itnecessary, on account of the complex shapes of wall portions of theintake duct, to use complex cores comprising a plurality of parts sothat they can be released from the molded shapes, but without thepossibility of avoiding the formation of plastic burrs at the partingplanes of the part [sic] of the core. It is therefore impossible to moldsuch throttle valve bodies to their directly usable shape withoutfinishing machining or deburring.

The object of the present invention is to provide a throttle valve bodywhich meets practical requirements better than those previously known,particularly in that it makes it possible to obtain the requisiteopening progressiveness, while being capable of being produced bymolding from synthetic material, without having the abovementioneddisadvantages, that is to say while being capable of being obtaineddirectly in the ultimate usable shape, without any particular difficultyin removal from the mold or any particular complexity in the productionof the mold.

To achieve this object, the invention provides a throttle valve body ofthe type defined above and known from FR-A-2,694,963, and which ischaracterized in that said evolutive surface portion of complex shape,which cooperates with the flap side in the form of a flat half diskwhich rotates respectively upstream and downstream during opening, has,at each level along the axis of the intake duct and over half the crosssection of the duct on the same side of the axis of the duct as the flapside in the form of a flat half disk, a cross section substantially inthe form of a half ellipse, of which the minor semiaxis, perpendicularlyto the axis of rotation, decreases progressively as far as a definiteopening angle of the flap, whilst, respectively upstream and downstreamof this evolutive surface portion and over the same half of the crosssection of the duct, as well as over the other half of the cross sectionof the duct, on the flap side which rotates respectively downstream andupstream during opening and as far as the level, along the axis of theintake duct, which corresponds respectively to the downstream andupstream edge of said evolutive surface portion, the wall of the duct isrespectively convergent and divergent, that flap side which rotatesrespectively downstream and upstream during opening having respectivelyon its upstream and downstream face a shoulder, the edge of which has aprofile selected so as to slow the increase in the passage cross sectionduring the initial opening of the flap, with respect to a flap side inthe form of a flat half disk rotating respectively downstream andupstream in a cylindrical duct, the intake duct having, respectivelydownstream and upstream of the minimum opening position of the flap, aportion respectively downstream and divergent to the outlet of the ductand upstream and convergent from the inlet of the duct.

By combining an evolutive shape of the intake duct, said shape beinglimited to a part located respectively upstream or downstream of theaxis of rotation of the flap and on that side of the flap which rotatesrespectively upstream or downstream during opening, with a flap, ofwhich the side rotating respectively downstream or upstream has ashoulder, it is possible to preserve the advantages of the embodimentswith progressive opening of the prior art, whilst at the same timehaving an intake duct, of which the portion respectively downstream orupstream of the minimum opening position of the flap is respectivelydivergent to the outlet of the duct or convergent from the inlet of thelatter, thus making the housing of the throttle valve body easy toremove from the mold, particularly when this respectively divergent orconvergent portion has a circular cross section of a diameter varyingmonotonically from upstream in a downstream direction.

Advantageously, in the minimum opening position of the flap, the latteris arranged in a straight cylindrical central portion of circular crosssection of the intake duct, said central portion being substantiallysymmetrical along the axis of the intake duct on either side of the axisof rotation, so that the flap, preferably of slightly elliptic shape,can be laid with its edge against the wall of the duct in thiscylindrical central portion in the case of an inclination of the flaprelative to a plane transverse to the axis of the duct which isapproximately 5° and without the risk of the flap being jammed.

To make it easier to remove the housing from the mold, the respectivelydivergent downstream or convergent upstream portions of the intake ductare advantageously frustoconical from the respectively downstream andupstream edge of said cylindrical central portion respectively as far asthe outlet and inlet of the intake duct, the half angle at the vortex ofthe frustoconical shape being capable of being selected so as tocorrespond to a favorable mold release angle. The clearance produced inthis way in the duct makes it easier to mount a flap which is thickenedlocally, for example at the center, for the passage or incorporation ofan axis of rotation, or on an edge.

For the same reason, and to make it possible to introduce and installthe flap in the intake duct, parallel to the plane defined by the axisof the duct and the axis of rotation, on automatic assembly lines, therespectively convergent and divergent portion of that half of the wallof the intake duct which is respectively upstream and downstream of theminimum opening position of the flap and on the same side of the axis ofrotation as the flap side which rotates respectively downstream andupstream during opening is advantageously a frustoconical surfaceportion convergent respectively from the inlet and the outlet of theduct respectively as far as the upstream and downstream edge of thecylindrical central portion, so that the diameter of the intake duct inthe above-defined plane in which the flap is introduced always remainsgreater than the diameter of the flap.

In a simple embodiment, the shoulder on one face of the flapadvantageously has a shape substantially of an ellipsoidal cap which hasa major axis substantially parallel to the axis of rotation, butslightly offset in the downstream direction of the latter, and theperiphery of which is connected to the edge of the flap side rotatingrespectively downstream and upstream. The flap may thus be produced fromsynthetic material, for example thermoplastic, and comprise a flat disk,to which said shoulder is molded or attached, for example secured byultrasonic welding, the shoulder being capable, for example, of beingformed by a cup delimiting a closed space or of being molded togetherwith the flap, at the same time delimiting a space open downstream inthe duct.

The housing, together with its intake duct, may likewise be molded inone piece to the ultimate shape from a synthetic material, for examplethermoplastic.

The invention will be understood better from a reading of the followingdescription of particular embodiments given by way of nonlimitingexamples with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view in axial section, perpendicularly to theaxis of rotation, of an example with a shoulder in the form of a closedcup on the upstream face of the flap half rotating downstream to thestart of opening,

FIGS. 2 and 3 are views, similar to that of FIG. 1, of two variantsrespectively with a shoulder in the form of a cup open downstream andwith a solid shoulder, and

FIG. 4 is a view, similar to that of FIG. 3, of a variant symmetricalwith respect to the axis of rotation, the airflow always coming from thetop of the figure.

In FIG. 1, the throttle valve body 1 comprises a housing 2 produced bymolding from a synthetic material, such as a thermoplastic, and obtainedin its ultimate shape without any additional machining or deburring. Anintake duct 3 of longitudinal axis 4 is formed in the housing 2.

A shaft 5 perpendicular to the longitudinal axis 4 of the duct 3 andintersecting this axis 4 is mounted pivotably in the housing 2 and formsthe center axis of rotation transverse to the duct 3 for a flap 6.

The rotary shaft 5 is mounted pivotably in a central portion 7 of theduct 3. In this central portion 7, the wall of the duct 3 is a straightcylindrical wall of circular cross section, which extends substantiallysymmetrically on either side of the rotary shaft 5 along thelongitudinal axis 4 of the duct 3. Downstream of the downstream edge 8of the central portion 7, the duct 3 has a divergent downstream portion9 which is frustoconical from the downstream edge 8 as far as the outlet10 of the duct 3, at the bottom in FIG. 1. In this divergent downstreamportion 9, the cross section of the duct 3 is therefore circular with aradius progressively increasing monotonically from upstream in adownstream direction.

Upstream of the upstream edge 11 of the central portion 7, the wall ofthe duct 3 is dissymmetric with respect to the diametrical plane passingthrough the axis 4 of the duct 3 and the center of the rotary shaft 5.Over half of the cross section of the duct 3, said half being located onthe right of the rotary shaft 5 in FIG. 1, the wall of the duct 3 isdefined by a frustoconical surface portion 12 which is coaxial to theaxis 4, in the same way as the downstream divergent 9, but whichconverges from the inlet 13 of the duct 3, in the top part of FIG. 1, asfar as the upstream edge 11 of the cylindrical central portion 7.

In the other half of the cross section of the duct 3, on the left of theaxis 4 and of the rotary shaft 5 in FIG. 1, the wall of the duct 3 isdelimited by an evolutive surface portion 14 of complex shape, whichextends upstream of the upstream edge 11 of the central portion 7 as faras a position opposite the edge of the flap 6 when the latter ininclined at a particular angle of between approximately 30° andapproximately 50° to the transverse plane perpendicular to the axis 4 ofthe duct 3 and passing through the center of the rotary shaft 5, and,upstream of this evolutive surface portion 14, the wall of the duct 3 isdelimited by a convergent surface portion 15 which converges from theinlet 13 of the duct 3.

In the evolutive surface portion 14, the corresponding cross sectionalhalf of the duct 3 has a substantially semielliptic shape which evolvesprogressively from a semicircular shape at the upstream edge 11 of thecentral portion 7 as far as a semielliptic half cross section of smallerminor semiaxis at the connection between the evolutive surface portion14 and the convergent surface portion 15. In other words, at each levelalong the axis 4 of the duct 3 upstream from the upstream edge 11 of thecentral portion 7 and as far as the level at which the evolutive surfaceportion 14 is connected to the convergent surface portion 15, thecorresponding half cross section of the duct 3 has the shape of a halfellipse, of which the minor semiaxis, perpendicularly to the rotaryshaft 5, decreases progressively, whilst its major axis remains constantand equal to the diameter of the cylindrical central portion 7.

The flap 6, advantageously made from a synthetic material, such as athermoplastic, consists of a substantially circular or slightly ellipticdisk 16 having a generally constant thickness, but being capable ofcomprising reinforcing ribs, passing through a diametrical slot of therotary shaft 5, and that side of the flap 6 which rotates downstreamduring the opening of the flap, that is to say, bearing in mind thedirection of rotation of the flap during opening which is indicated byan arrow in FIG. 1, the flap half on the right of the shaft 5 in thisFIG. 1, is a flat half disk having, on its upstream face, a shoulder 17molded preferably from the same synthetic material as the flat disk 16and attached and secured, for example by ultrasonic welding, to the halfdisk, which rotates downstream during the opening of the flap 6, so asto delimit a closed space. This shoulder 17 consists of a cup whichprojects in the upstream direction of the duct 3 and the downstreamperiphery of which is connected to the downstream edge of the half diskof the flap 6, said half disk rotating downstream during opening. Thatwall of the cup 17 which is opposite the wall of the duct 3 hassubstantially the shape of an ellipsoidal cap, the major axis of whichis parallel to the rotary shaft 5, is offset by a short distancedownstream of this shaft 5 and is slightly smaller than the diameter ofthe central portion 7 and the minor axis of which is selected so as togive this wall of the shoulder 17 a profile which, together with theopposite profile of the wall of the duct 3, delimits a passage crosssection for the air admitted to the engine, said passage cross sectionincreasing less rapidly, as compared with a flap in the form of a flatdisk rotating in a cylindrical duct, when the flap 6 opens from itsminimum opening position, in which the flat disk 16 and the essentialpart of the shoulder 17 are accommodated in the cylindrical centralportion 7, into a position such that the flat disk 16 is inclined a fewdegrees to the transverse plane perpendicular to the axis 4 and passingthrough the center of the rotary shaft 5. Thus, the half disk carryingthe shoulder 17 and rotating downstream during opening is slightlyinclined downstream, whilst, on the opposite side of the shaft 5, theflat half disk, without a shoulder, rotating upstream during the openingof the flap 6, is slightly inclined upstream. The profile of the edge ofthe shoulder 17 is selected so as to allow the half disk carrying theshoulder to rotate downstream, without the shoulder 17 being in contactwith the wall of the duct 3.

In the axial section of FIG. 1, the flap 6 is illustrated in anintermediate position between its minimum opening position and itsmaximum opening position, in which the flat disk 16 of the flap 6 isoriented substantially parallel to the axis 4 of the duct 3. In thisintermediate position, in which the opening angle of the flap 6 issmaller than the given maximum angle of inclination for defining theevolutive surface 14, that side of the flap 6 which is in the form of aflat half disk and which rotates upstream during the opening of the flapcooperates via its upstream edge with this evolutive surface 14 so as todefine, between the latter and the upstream edge of the flap 6, apassage cross section for the air (circulating from the top downward inthe figures), said passage cross section increasing as a function of theopening angle less rapidly than in the case of a flap in the form of aflat disk rotating in a cylindrical duct, as long as the flap 6 is inthe initial opening phase, in which its upstream edge is displacedopposite the evolutive surface 14.

It will be understood that, by selecting the profile of the shoulder 17,on the one hand, and selecting the profile of the evolutive surface 14opposite the upstream flat half disk of the flap 6, it is possible toobtain virtually any desired low of variation of the airflow as afunction of the opening angle of the flap 6 in a throttle valve body 1,the housing 2 of which has an intake duct 3 having a shape which makesit easy to remove from the mold. In the example of FIG. 1, theseadvantages are afforded by the combination of a flap, of which the edgerotating downstream is shouldered, with a duct, the wall of which has anevolutive surface portion of complex shape limited to a surface partlocated upstream of the axis of rotation of the flap and opposite theflap edge rotating upstream.

The variant of FIG. 2 differs from the example of FIG. 1 only in theproduction of the shoulder which is a cup 17' molded in one piece withthe flap 6' so as to delimit, in the half flap pivoting downstreamduring opening, a space which is open downstream in the duct 3 and whichhas the same shape as in FIG. 1, so that identical references are usedto denote parts of identical shape.

Likewise, the variant of FIG. 3 differs from FIGS. 1 and 2 only in theproduction of the shoulder 17" which is solid and molded and attached tothe upstream face of the half disk 16 pivoting downstream during openingor, if appropriate, is molded in one piece with this disk half 16 toform the flap 6". The housing 2 and its duct 3 are otherwise identical.

Finally, the variant of FIG. 4 is symmetrical to that of FIG. 3 withrespect to the rotary shaft 5, but the airflow always circulates fromthe top downward in the figure. Consequently, the shoulder 17a is on thedownstream face of that half of the disk 16a of the flap 6a which pivotsupstream during opening, whilst the other half of the disk 16a, whichother half pivots downstream during opening, is displaced opposite theevolutive surface 14a, downstream of the downstream edge 11a of thestraight and circular cylindrical central portion 7a of the duct 3a.Downstream of the downstream edge 11a and of the evolutive surface 14a,the duct 3a has respectively a frustoconical divergent 12a and adivergent 15a on the corresponding halves of the cross section whichextend as far the outlet 13a of the duct 3a. Upstream of the upstreamedge 8a of the central portion 7a, the duct 3a has a frustoconicalconvergent 9a from its inlet 10a in the housing 2a of the throttle valvebody 1a.

This variant has the same advantages as the preceding ones as regardsthe ease with which molding is carried out and progressiveness in thevariation of the airflow. However, it may prove slightly unfavorable interms of turbulence under some conditions of use.

We claim:
 1. A throttle valve body for a fuel injection device of aninternal combustion engine, said body comprising:a housing in which anair intake duct is formed and a flap having the form of a substantiallycircular disk said flap being mounted on a central rotation shaftextending transversely with regard to said duct, said flap beingdisplaceable by pivoting with said rotation shaft on an opening anglebetween a minimum opening position and a maximum opening position inwhich said flap is oriented substantially parallel to an axis of saidduct, said flap having a first side part which rotates upstream fromsaid minimum opening position, said first side-part being substantiallyin the form of a flat half disk and said intake duct having a wallwhich, on the same side as said flap first side-part and upstream ofsaid minimum opening position of said flat, has an evolutive surfaceportion cooperating with said flap first side part, such that, at thestart of an opening displacement of said flap, a passage delimitedbetween said flap and said evolutive surface portion has a cross sectionincreasing as a function of said opening angle less rapidly than in thecase of a cylindrical air intake duct, wherein said evolutive surfaceportion has, at each level along said duct axis and over a first ductcross section half which extends on the same side of said duct axis assaid flap first side part, a cross section substantially in the form ofa half ellipse, having a minor semiaxis, perpendicularly to saidrotation shaft, which decreases progressively as for as definite openingangle of said flap, while upstream of said evolutive surface portion andover said first duct cross section half, as well as over a second ductcross section half on the same side as a second side part of said flapwhich rotates downstream during opening and as far as a level position,along said duct axis, which corresponds to a downstream edge of saidevolutive surface portion, said duct has a wall which is convergent,said flap second side part having an upstream face on which thereprotrudes a shoulder with an edge having a profile selected so as toslow the increase of said passage cross section during the initial flapopening, with respect to a flap second side part in the form of a flathalf disk rotating downstream in a cylindrical duct, said intake having,downstream of said minimum opening position of said flap, a downstreamand divergent portion as far as an outlet of said duct.
 2. The throttlevalve body according to claim 1, wherein in said minimum openingposition of said flap, said flap is arranged in a straight cylindricalcentral portion of circular cross section of said intake duct, saidcentral portion being substantially symmetrical along said duct axis oneither side of said rotation shaft.
 3. The throttle valve body accordingto claim 2, wherein said divergent downstream portion of said intakeduct is frustoconical from a downstream edge of said cylindrical centralportion as far as said outlet of said intake duct.
 4. The throttle valvebody according to claim 2, wherein said convergent portion of a half ofthe wall of said intake duct which is upstream of said minimum openingposition of said flap and on the same side of the rotation shaft as saidflap second side part during opening is a frustoconical surface portionconvergent from an inlet of said duct as far as an upstream edge of saidcylindrical central portion.
 5. The throttle valve body according toclaim 1, wherein said housing, together with said intake duct, is moldedin one piece to the ultimate shape from a synthetic material.
 6. Thethrottle valve body according to claim 1, wherein said shoulderprotruding on said upstream face of said flap has a shape substantiallyof an ellipsoidal cap which has a major axis substantially parallel tosaid rotation shaft and slightly offset in the downstream direction ofsaid shaft, and wherein said shoulder has a periphery which is connectedto an edge of said flap second side part.
 7. The throttle valve bodyaccording to claim 6, wherein said flap is made of synthetic materialand comprises a flat disk integrally made with said shoulder.
 8. Thethrottle valve body according to claim 7, wherein said shoulder isformed by a cup delimiting a closed space.
 9. The throttle valve bodyaccording to claim 7, wherein said shoulder is formed by a cup moldedtogether with said flap and delimiting a space open downstream in theduct.